package network;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        ExecutorService pool = Executors.newCachedThreadPool();
        while (true) {
            // 通过 accept 方法来 "接听电话" , 然后才能进行通信
            Socket clientSocket = serverSocket.accept();
//            Thread t = new Thread(()-> {
//                processConnection(clientSocket);
//            });
//            t.start();

            pool.submit(new Runnable() {
                @Override
                public void run() {
                    processConnection(clientSocket);
                }
            });
        }
    }

    // 通过这个方法来处理一次连接. 连接建立的过程中就会涉及到多次的请求响应交互.
    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s:%d] 客户端上线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
        // 循环读取客户端的请求并返回响应
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()) {
            Scanner scanner = new Scanner(inputStream);
            while (true) {
                if (!scanner.hasNext()) {
                    // 读取完毕. 客户端断开连接就会产生读取完毕.
                    System.out.printf("[%s:%d] 客户端下线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
                    break;
                }
                // 1.读取请求并解析, 这里注意隐藏的约定, next 读的时候要读到空白符才会结束.
                //   因此就要求客户端发来的请求必须带有空白符结尾. 比如 \n 或者空格.
                String request = scanner.next();
                // 2.根据请求计算响应
                String response = process(request);
                // 3. 把响应返回客户端
                //    通过这种方式可以写回,但是这种方式不方便给返回的响应中添加 \n
                // outputStream.write(response.getBytes(), 0, response.getBytes().length);
                //    也可以给 outputStream 套上一层, 完成更方便的写入.
                PrintWriter printWriter = new PrintWriter(outputStream);
                printWriter.println(response);
                printWriter.flush();

                System.out.printf("[%s:%d] req: %s, resp: %s\n", clientSocket.getInetAddress(), clientSocket.getPort(),
                        request, response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer server = new TcpEchoServer(9090);
        server.start();
    }
}


